Method for producing optical sheet, optical sheet, and method for producing lenticular lens sheet

Abstract

The present invention aims at providing a manufacturing method for an optical sheet capable of manufacturing a thin optical sheet of a uniform thickness distribution with a high thickness accuracy, and high shaping / transferring performances, and an optical sheet manufactured by using the manufacturing method. A manufacturing method for an optical sheet according to the present invention includes passing a resin discharged from a die between a touch roll and a shaping roll under pressure.

Description

TECHNICAL FIELD [0001] The present invention relates to a manufacturing method for an optical sheet, an optical sheet, and a manufacturing method for a lenticular lens sheet. BACKGROUND ART [0002] In conventional manufacturing methods for an optical sheet, a sheet resin material extruded from an extrusion die is passed under pressure through a gap between a pair of engraved roll and mirror-finished metal roll to manufacture a resin sheet. With such a manufacturing method, it is necessary to use a rigid roll with the pressing force allowing some uniform sheet thickness to manufacture a sheet with any optical performance. It is also necessary to transfer a reverse pattern engraved on a mold roll onto a sheet to create the smooth surface or particular surface shape as is necessary for exhibiting an optical performance, at some shaping rate. [0003] In recent years, there is a growing demand for thinner optical sheets in response to needs to downsize the lens to shorten a focal distance ...

AI Technical Summary

Benefits of technology

[0023] The present invention provides a manufacturing method for an optical sheet for passing a thermoplastic resin discharged from a die between a touch roll and a shaping roll under pressure to manufacture an optical sheet, wherein a temperature of the resin discharged from the die is in a range of 2500 to 290° C., a molding speed is in a range of 8 to 40 m / min., and an air gap between the die and a nip position between the touch roll and the shaping roll is 110 mm or smaller. The touch roll is an elastic roll deformable in a diameter direction by 0.01% or more of a diameter under a linear pressure of 30 kg / cm. According to the manufacturing method, a thin optical sheet of a uniform thickness distribution can be formed with a high thickness accuracy, and high shape and transfer fidelity.

[0028] The present invention provides a manufacturing method for a lenticular lens sheet, including: a step of forming a lenticular lens sheet having a thickness of 350 μm or less through extrusion molding; a step of forming a photosensitive layer on a flat surface of the lenticular lens sheet; and a step of forming a light-shielding pattern by irradiating the photosensitive layer with light from a lenticular lens side of the lenticular lens sheet to form a cured portion and an uncured portion by use of light focused through the lenticular lens. According to the manufacturing method, a low-cost, high-quality lens sheet can be formed.

[0031] Further, the lenticular lens sheet is manufactured passing a thermoplastic resin discharged from a die between a touch roll and a shaping roll under pressure, in the step of forming the lenticular lens sheet, a temperature of the resin discharged from the die is in a range of to 250° to 290° C., a molding speed is in a range of to 8 to 40 m / min., an air gap between the die and a nip position between the touch roll and the shaping roll is 110 mm or smaller, and the touch roll is an elastic roll deformable in a diameter direction by 0.01% or more of a diameter under a linear pressure of 30 kg / cm. According to the manufacturing method, a thin optical sheet of a uniform thickness distribution can be formed with a high thickness accuracy, and high shaping / transferring performances.

[0032] A lens sheet according to the present invention is manufactured by using the manufacturing method for a lens sheet. The lens sheet thus manufactured costs low, and attains high quality.

Problems solved by technology

However, with the manufacturing method based on the extrusion molding, it is difficult to produce a thin sheet having such a shape that gives an optical performance sufficient for optical use, with a high thickness accuracy.

This is because the contact between a roll and a resin gets worse owing to an unbalanced relation between a resin pressure and a pressing force / rigidity of a roll, which causes the roll to deform on the thin sheet requiring a high thickness accuracy, and the deformed roll cannot press the central portion of the sheet, making it impossible to attain such a thickness distribution that realizes the uniform optical performance.

To that end, the roll hardly produces an optical functional sheet with a shaping rate and transfer accuracy high enough for optical usage.

Further, there have not been made extensive efforts to transfer a desired lens shape with the method of manufacturing a smooth sheet using this elastic roll based on the common belief that the resin is cooled and solidified on contact with a mold roll, and sufficient transferability cannot be achieved unless the resin is applied with enough pressure upon molding.

In particular, conventional manufacturing methods for an optical sheet hardly produce an optical sheet satisfying all of conditions such as the thickness of 300 μm or smaller, a pitch of 300 μm or smaller, and the mold height of 30 μm or larger.

With the aforementioned manufacturing methods for an optical sheet, the shape that gives an optical performance can be transferred with the use of a rigid roll, but a thin film of a uniform thickness distribution is difficult to form with a high thickness accuracy.

A thin sheet of a uniform thickness distribution can be produced with a high thickness accuracy by use of an elastic roll, but it is impossible to attain shaping / transferring performances enough for optical use.

As a result, the high thickness accuracy for the optical sheet and the high shaping / transferring performances could not be both fulfilled at the same time.

In manufacturing the lenticular lens sheet 102 using the 2P resin in the above manner, there arises a problem of an increase in production cost for a rear projection screen due to the expensive 2P resin.

There is another problem in that the productive facility for the lenticular lens sheet 102 is complicated because the transparent supporting member 1022 is formed and then, the lens portion 1021 is formed thereon.

Moreover, in the case of using the 2P resin, the lens portion 1021 differs from the transparent supporting member 1022 in material, which leads to poor environmental stability, and causes a lenticular lens sheet 1 to warp.

The difference in refractive index between them causes color unevenness or limits the transparency in some cases.

Further, since the lens portion 1021 and the transparent supporting member 1022 are different in material, edge blunting easily occurs, and there is a limitation on the shaping performance.

As mentioned above, with the conventional manufacturing methods for an optical sheet, the shape that gives an optical performance can be transferred with the use of a rigid roll, but a thin film of a uniform thickness distribution is difficult to form with a high thickness accuracy.

A thin sheet of a uniform thickness distribution can be produced with a high thickness accuracy by use of an elastic roll, but it is impossible to attain shaping / transferring performances enough for optical use.

As a result, the high thickness accuracy for the optical sheet and the high shaping / transferring performances could not be both fulfilled at the same time.

Besides, the conventional manufacturing method for the lenticular lens sheet has a problem that two different materials are used and therefore, a low-cost, high-quality lenticular lens sheet cannot be formed.

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